Phalaenopsis attract a great deal of public attention. For cultivation of plants, recently, mass-production of plants through clonal propagation is being in full flood. To the induction of protocorm-like bodies (PLB) that are in the initial stage for the production of clonal plants, at present, applied are conventional leaf segment culture and also other spike-axillary bud culture and root tip culture (M. Tanaka, 1987, Studies on the Clonal Propagation of Phalaenopsis through in-vitro Culture, Memoirs of Faculty of Agriculture, Kagawa University, No. 49; 1-85; S. Ichihashi, 1992, Micropropagation of Phalaenopsis through the Culture of Lateral Buds from Young Flower Stalks, Lindleyana, 7(4): 208-215; M. Kobayashi, M. Komatsuda & S. Yoneuchi, 1990, Studies on the vegetative propagation of Phalaenopsis through root tip culture, J. J. Soc. Hort. Sci., 63(suppl.2); 664-671).
However, in the process of the induction of PLB through such known root tip culture (M. Kobayashi, M. Komatsuda & S. Yoneuchi, 1990, Studies on the vegetative propagation of Phalaenopsis through root tip culture, J. J. Soc. Hort. Sci., 63(suppl.2); 664-671) or any other culture, the degree of the intended induction is often low or, as the case may be, no induction is attained for some varieties, hybrids and materials.
Because of such unsure induction of PLB, mass-production of plants through clonal propagation could not apply to some varieties and hybrids of Phalaenopsis. Therefore, in order to improve the efficiency in the induction of PLB, it is necessary to establish an effective method of initial culture capable of overcoming the difference in varieties and hybrids and the difference in materials.
The reasons for such unsure induction of PLB in known root tip culture are believed to be essentially that the surface of the meristematic tissue of a root tip, which is a material of a PLB-forming source, will be often damaged while being sterilized, and that said tissue could not satisfactorily display its ability for cell division due to conditions and methods unsuitable for cultivating it thereby resulting in that its ability to form PLB is lowered.